Journal of Oceanography

, Volume 63, Issue 2, pp 293–307 | Cite as

Temporal variability of winter mixed layer in the mid-to high-latitude North Pacific

Original Papers

Abstract

Temperature and salinity data from 2001 through 2005 from Argo profiling floats have been analyzed to examine the time evolution of the mixed layer depth (MLD) and density in the late fall to early spring in mid to high latitudes of the North Pacific. To examine MLD variations on various time scales from several days to seasonal, relatively small criteria (0.03 kg m−3 in density and 0.2°C in temperature) are used to determine MLD. Our analysis emphasizes that maximum MLD in some regions occurs much earlier than expected. We also observe systematic differences in timing between maximum mixed layer depth and density. Specifically, in the formation regions of the Subtropical and Central Mode Waters and in the Bering Sea, where the winter mixed layer is deep, MLD reaches its maximum in late winter (February and March), as expected. In the eastern subarctic North Pacific, however, the shallow, strong, permanent halocline prevents the mixed layer from deepening after early January, resulting in a range of timings of maximum MLD between January and April. In the southern subtropics from 20° to 30°N, where the winter mixed layer is relatively shallow, MLD reaches a maximum even earlier in December–January. In each region, MLD fluctuates on short time scales as it increases from late fall through early winter. Corresponding to this short-term variation, maximum MLD almost always occurs 0 to 100 days earlier than maximum mixed layer density in all regions.

Keywords

Winter mixed layer North Pacific temporal variability Argo 

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References

  1. Akima, H. (1970): A new method of interpolation and smooth curve fitting based on local procedures. J. Assoc. Comput. Meth., 17, 589–603.Google Scholar
  2. Argo Data Management Team (2002): Report of the Argo Data Management Meeting. Proc. Argo Data Management Third Meeting, Marine Environmental Data, Ottawa, ON, Canada, 42 pp.Google Scholar
  3. Argo Data Management Team (2004): Argo quality control manual, version 2.0b. Argo Data Management, 26 November 2004, 23 pp.Google Scholar
  4. Argo Science Team (2000): Report of the Argo Science Team Second Meeting. Proc. Argo Science Team Second Meeting, Southampton Oceanography Centre, Southampton, U.K., 35 pp.Google Scholar
  5. Argo Science Team (2001): Argo: The global array of profiling floats. p. 248–258. In Observing the Oceans in the 21st Century, ed. by C. J. Koblinsky and N. R. Smith, GODAE Project Office, Bureau of Meteorology, Melbourne.Google Scholar
  6. Bathen, K. H. (1972): On the seasonal changes in the depth of the mixed layer in the North Pacific Ocean. J. Geophys. Res., 77, 7138–7150.Google Scholar
  7. Bingham, F. M. (1992): Formation and spreading of Subtropical Mode Water in the North Pacific. J. Geophys. Res., 97, 11,177–11,189.Google Scholar
  8. Cannon, G. A. (1966): Tropical waters in the western Pacific Oceans, August–September 1957. Deep-Sea Res., 13, 1139–1148.Google Scholar
  9. Cokelet, E. D. and P. J. Stabeno (1997): Mooring observations of the thermal structure, salinity, and currents in the SE Bering Sea basin. J. Geophys. Res., 102, 22947–22964.Google Scholar
  10. Conkright, M., S. Levitus, T. O’Brien, T. Boyer, J. Antonov and C. Stephens (1998): World Ocean Atlas 1998, CD-ROM data set documentation. NODC Tech. Rep. 15, Silver Spring, MD, 16 pp.Google Scholar
  11. Conkright, M. E., R. A. Locarnini, H. E. Garcia, T. D. O’Brien, T. P. Boyer, C. Stephens and J. I. Antonov (2002): World Ocean Atlas 2001: Objective analysis, data statistics, and figures, CD-ROM documentation. National Oceanographic Data Center, Silver Spring, MD, 17 pp.Google Scholar
  12. da Silva, A. M., C. C. Young and S. Levitus (1994): Algorithms and Procedures. Vol. 1, Atlas of Surface Marine Data 1994. NOAA Atlas NESDIS, 83 pp.Google Scholar
  13. de Boyer Montégut, C., G. Madec, A. S. Fischer, A. Lazar and D. Iudicone (2004): Mixed layer depth over the global ocean: An examination of profile data and a profile-based climatology. J. Geophys. Res., 109, C12003, doi:10.1029/2004JC002378.Google Scholar
  14. Freeland, H. J. and P. F. Cummins (2005): Argo: A new tool for environmental assessment and monitoring of the world’s oceans, an example from the N.E. Pacific. Prog. Oceanogr., 64, 31–44.CrossRefGoogle Scholar
  15. Freeland, H. J., K. L. Denman, C. S. Wong, F. Whitney and R. Jacques (1997): Evidence of change in the winter mixed layer in the Northeast Pacific Ocean. Deep-Sea Res., 44, 2117–2129.CrossRefGoogle Scholar
  16. Hanawa, K. and L. D. Talley (2001): Mode waters. p. 373–386. In Ocean Circulation and Climate, ed. by J. Church et al., Academic Press.Google Scholar
  17. Hanawa, K. and Y. Toba (1981): Terms governing temperature and thickness of the oceanic mixed layer and their estimates for sea area south of Japan. Tohoku Geophys. J., 28, 161–173.Google Scholar
  18. Hautala, S. L. and D. H. Roemmich (1998): Subtropical mode water in the Northeast Pacific basin. J. Geophys. Res., 103, 13055–13066.Google Scholar
  19. Huang, R. X. and B. Qiu (1994): Three-dimensional structure of the wind-driven circulation in the subtropical North Pacific. J. Phys. Oceanogr., 24, 1608–1622.CrossRefGoogle Scholar
  20. Iwasaka, N., F. Kobashi, Y. Kinoshita and Y. Ohno (2006): Seasonal variations of the upper ocean in the western North Pacific observed by an Argo float. J. Oceanogr., 62, 481–492.CrossRefGoogle Scholar
  21. Kara, A. B., P. A. Rochford and H. E. Hurlburt (2000): Mixed layer depth variability and barrier layer formation over the North Pacific Ocean. J. Geophys. Res., 105, 16783–16801.Google Scholar
  22. Kara, A. B., P. A. Rochford and H. E. Hurlburt (2003): Mixed layer depth variability over the global ocean. J. Geophys. Res., 108, 3079, doi:10.1029/2000JC000736.CrossRefGoogle Scholar
  23. Kistler, R., E. Kalnay, W. Collins, S. Saha, G. White, J. Woollen, M. Chelliah, W. Ebisuzaki, M. Kanamitsu, V. Kousky, H. van den Dool, R. Jenne and M. Fiorino (2001): The NCEP-NCAR 50-year reanalysis: Monthly means CDROM and documentation. Bull. Amer. Meteor. Soc., 82, 247–268.CrossRefGoogle Scholar
  24. Ladd, C. A. and L. Thompson (2000): Formation mechanisms for North Pacific central and eastern subtropical mode waters. J. Phys. Oceanogr., 30, 868–887.CrossRefGoogle Scholar
  25. Levitus, S. (1982): Climatological Atlas of the World Ocean. NOAA Prof. Paper 13, 173 pp.Google Scholar
  26. Lukas, R. and E. Lindstrom (1991): The mixed layer of the western equatorial Pacific Ocean. J. Geophys. Res., 96, 3343–3357.CrossRefGoogle Scholar
  27. Marshall, J. C., A. J. G. Nurser and R. G. Williams (1993): Inferring the subduction rate and period over the North Atlantic. J. Phys. Oceanogr., 23, 1315–1329.CrossRefGoogle Scholar
  28. Masumoto, Y., H. Sasaki, T. Kagimoto, N. Komori, A. Ishida, Y. Sasai, T. Miyama, T. Motoi, H. Mitsudera, K. Takahashi, H. Sakuma and T. Yamagata (2004): A fifty-year eddy-resolving simulation of the world ocean: Preliminary outcomes of OFES (OGCM for the Earth Simulator). J. Earth Simulator, 1, 35–56.Google Scholar
  29. Masuzawa, J. (1969): Subtropical Mode Water. Deep-Sea Res., 16, 463–472.Google Scholar
  30. Miura, T., T. Suga and K. Hanawa (2003): Numerical study of formation of dichothermal water in the Bering Sea. J. Oceanogr., 59, 369–376.CrossRefGoogle Scholar
  31. Monterey, G. and S. Levitus (1997): Seasonal Variability of Mixed Layer Depth for the World Ocean. NOAA Atlas NESDIS 14, 100 pp.Google Scholar
  32. Nakamura, H. (1996): A pycnostad on the bottom of the ventilated portion in the central subtropical North Pacific: Its distribution and formation. J. Oceanogr., 52, 171–188.CrossRefGoogle Scholar
  33. Ohno, Y., T. Kobayashi, N. Iwasaka and T. Suga (2004): The mixed layer depth in the North Pacific as detected by the Argo floats. Geophys. Res. Lett., 31, L11306, doi:10.1029/2004GL019576.Google Scholar
  34. Oka, E. (2005): Long-term sensor drift found in recovered Argo profiling floats. J. Oceanogr., 61, 775–781.CrossRefGoogle Scholar
  35. Oka, E. and K. Ando (2004): Stability of temperature and conductivity sensors of Argo profiling floats. J. Oceanogr., 60, 253–258.CrossRefGoogle Scholar
  36. Oka, E. and T. Suga (2003): Formation region of North Pacific subtropical mode water in the late winter of 2003. Geophys. Res. Lett., 30, 2205, doi:10.1029/2003GL018581.CrossRefGoogle Scholar
  37. Oka, E. and T. Suga (2005): Differential formation and circulation of North Pacific Central Mode Water. J. Phys. Oceanogr., 35, 1997–2011.CrossRefGoogle Scholar
  38. Qiu, B. and R. X. Huang (1995): Ventilation of the North Atlantic and North Pacific: Subduction versus obduction. J. Phys. Oceanogr., 25, 2374–2390.CrossRefGoogle Scholar
  39. Sprintall, J. and D. Roemmich (1999): Characterizing the structure of the surface layer in the Pacific Ocean. J. Geophys. Res., 104, 23297–23311.Google Scholar
  40. Stommel, H. M. (1979): Determination of water mass properties of water pumped down from Ekman layer to the geostrophic flow below. Proc. Natl. Acad. Sci. USA., 76, 3051–3055.CrossRefGoogle Scholar
  41. Suga, T. and K. Hanawa (1990): The mixed layer climatology in the northwestern part of the North Pacific subtropical gyre and the formation area of Subtropical Mode Water. J. Mar. Res., 48, 543–566.Google Scholar
  42. Suga, T., Y. Takei and K. Hanawa (1997): Thermostad distribution in the North Pacific subtropical gyre: The central mode water and the subtropical mode water. J. Phys. Oceanogr., 27, 140–152.CrossRefGoogle Scholar
  43. Suga, T., A. Kato and K. Hanawa (2000): North Pacific Tropical Water: Its climatology and temporal changes associated with the climate regime shift in the 1970s. Prog. Oceanogr., 47, 223–256.CrossRefGoogle Scholar
  44. Suga, T., K. Motoki, Y. Aoki and A. M. Macdonald (2004): The Temporal Variability of Winter Mixed Layer 307 North Pacific climatology of winter mixed layer and mode waters. J. Phys. Oceanogr., 34, 3–22.CrossRefGoogle Scholar
  45. Takeuchi, E. (2006): Studies on the wintertime shoaling of oceanic surface mixed layer. Doctoral dissertation, Graduate School of Science, The University of Tokyo, 109 pp.Google Scholar
  46. Takeuchi, E. and I. Yasuda (2003): Wintertime shoaling of oceanic surface mixed layer. Geophys. Res. Lett., 30, 2152, doi:10.1029/2003GL018511.CrossRefGoogle Scholar
  47. Tully, J. P. (1964): Oceanographic regions and processes in the seasonal zone of the North Pacific Ocean. p. 68–84. In Studies on Oceanography, ed. by K. Yoshida, University of Tokyo Press, Tokyo.Google Scholar
  48. Uda, M. (1963): Oceanography of the subarctic Pacific Ocean. J. Fish. Res. Board Can., 20, 119–179.Google Scholar
  49. Uehara, H., T. Suga, K. Hanawa and N. Shikama (2003): A role of eddies in formation and transport of North Pacific Subtropical Mode Water. Geophys. Res. Lett., 30, 1705, doi:10.1029/2003GL017542.CrossRefGoogle Scholar
  50. Ueno, H., E. Oka, T. Suga and H. Onishi (2005): Seasonal and interannual variability of temperature inversions in the subarctic North Pacific. Geophys. Res. Lett., 32, L20603, doi:10.1029/2005GL023948.Google Scholar
  51. White, W. B. (1995): Design of a global observing system for gyre-scale upper ocean temperature variability. Prog. Oceanogr., 36, 169–217.CrossRefGoogle Scholar
  52. Wirts, A. E. and G. C. Johnson (2005): Recent interannual upper ocean variability in the deep southeast Bering Sea. J. Mar. Res., 63, 381–405.CrossRefGoogle Scholar
  53. Wong, A. and B. King (2005): Report on first Argo delayedmode QC workshop. First Argo delayed-mode QC workshop, 8–13 April 2005, Scripps Institute of Oceanography, La Jolla, San Diego, U.S.A., 27 pp.Google Scholar
  54. Wong, A. P. S., G. C. Johnson and W. B. Owens (2003): Delayed-mode calibration of autonomous CTD profiling float salinity data by theta-S climatology. J. Atoms. Ocean Technol., 20, 308–318.CrossRefGoogle Scholar
  55. Yasuda, I., T. Tozuka, M. Noto and S. Kouketsu (2000): Heat balance and regime shifts of the mixed layer in the Kuroshio Extension. Prog. Oceanogr., 47, 257–278.CrossRefGoogle Scholar
  56. Yuan, X. and L. D. Talley (1996): The subarctic frontal zone in the North Pacific: Characteristics of frontal structure from climatological data and synoptic surveys. J. Geophys. Res., 101, 16491–16508.Google Scholar

Copyright information

© The Oceanographic Society of Japan/TERRAPUB/Springer 2007

Authors and Affiliations

  1. 1.Institute of Observational Research for Global ChangeJapan Agency for Marine-Earth Science and TechnologyYokosuka, KanagawaJapan
  2. 2.Scripps Institution of OceanographyUniversity of CaliforniaSan Diego, La JollaU.S.A.
  3. 3.Department of Geophysics, Graduate School of ScienceTohoku UniversityAoba-ku, SendaiJapan
  4. 4.Ocean Research InstituteThe University of TokyoNakano-ku, TokyoJapan

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